Preheat oven to 375°F. Split the squash in half
lengthwise, remove the seeds, and place face-down on a lightly
oiled baking tray. Bake until very soft (30 to 40 minutes). Cool,
then scoop out the insides. Measure out 3 cups of squash, place it
in a food processor or blender with 1 1/2 cups of the orange juice,
and purée until smooth. (You may need to do this in batches.)
Transfer to a soup pot, and stir in the remaining orange
juice.

Melt the butter or heat the oil in a skillet, and add the
onion, ginger, salt, and spices. Sauté over medium heat until
the onion is very soft (about 8 minutes). Add a few tablespoons of
water, if necessary to prevent the spices from sticking.

Add the garlic and mushrooms, cover, and cook about 10 minutes
over medium heat, stirring occasionally.

Add the sauté to the squash mixture, scraping the skillet
well to salvage all the little tidbits of flavor. Add cayenne and
lemon juice to taste.